Mandrel for sanding drums

ABSTRACT

A mandrel for supporting large diameter sanding drums so that they are concentric and balanced. The structure comprises an inner cylinder-like member having heads in each end to which are secured supporting shafts. Slidably surrounding the inner member are metal cylinders having secured to their outer surfaces sleeves of rubber or the like. Spacer washers are interposed between the adjacent ends of the metal cylinders. Means is provided to exert compressive force on the rubber members, from each end of the mandrel, thus to cause the rubber sleeves to distort radially, frictionally securing the sanding drum to the mandrel.

Umted States Patent [1 1 [111 ,828,489

Culley, Jr. Aug. 13, 1974 [54] MANDREL FOR SANDING DRUMS PrimaryExaminer-Qthell M. Simpson [76] Inventor: Donnell H. Culley, Jr., Po.Box g g f l58l, Morristown, Tenn. 37814 p [22] Filed: Sept. 24, 1973[57] ABSTRACT [21] Appl' 400418 A mandrel for supporting large diametersanding drums so that they are concentric and balanced. The

[52] US. Cl 51/375 2/72 structure comprises an inner cylinder-likemember [51] Int. Cl B24d 9/02, B65 5/18 having heads in each end towhich are secured sup- [58] Field of Search 51/358, 372, 375; 242/72port shafts. Slidably surrounding the inner member References CitedUNITED STATES PATENTS 2,083,793 6/l937 Price .l 72 3,287,863 ll/l966Field 75 3,345,006 1 67 Gee 72 3,584,714 7l Rysw' 72 are m a1 cylindershaving secured to their outer surfaces sleeves of rub or the like.Spacer washers interposed between adjacent ends of the metal inders.Means is pr 'ded to exert co res force on th bber me rs, fro each ofmandrel, to cause the rub sleeves to distort radially, frictionallysecuring the sanding drum to the mandrel.

7 Claims, 4 Drawing Figures PAIENTEU MIG 1 31914 sum 1 or 2 MANDREL FORSANDING DRUMS This invention relates to improved mandrels for mountingsanding drums such as are commonly used in the woodworking arts.

In the art to which my invention relates it is now customary to usesanding drums which are cylinders of relatively thin steel or the likeon the outer surfaces of which carbide particles are copper brazed, thusto provide the abrasive surface. The thickness of the material of thesecylinders is on the order of 50/ 1000 of an inch and the diametersthereof may be on the order of 9 inches and in length from l6 to 60inches. These dimensions are given merely by way of example and are notintended to be the only sizes of saiding drums with which my inventionmay be used.

In using these cylinders it is necessary to provide a mandrel which willsupport them for rotation at fairly high speeds. At such speeds, it isdesired that they be concentrically mounted on the supporting mandrelwhich rotates them. In view of the thin wall sections involved it isdifficult to provide a mandrel which will hold these cylinders perfectlyconcentric and without local bulging of the surface of the same, due tothe internal supporting means. Furthermore, the supporting mandrel mustbe almost perfectly dynamically balanced because these relatively largecylinders'are run at considerable speeds, such for instance on the orderof 8,000 linear feet per minute.

With all the foregoing problems in mind, my invention contemplates amandrel for mounting sanding drums of the character indicated whichshall embody expandable rubber members which frictionally engage theinner surface of the sanding drum, together with means to expand theexternal diameter of the members uniformly throughout the length of themandrel, whereby the sanding drum is supported concentrically, withoutlocal bulging.

My invention contemplates the provision of a mandrel of the characterdesignated in which the expandable rubber section which engages theinner surface of the drum is divided, longitudinally, into a pluralityof separate, radially expandable rubber sections or sleeves.

My invention further contemplates a mandrel of the character designatedwhich, when the axially aligned separate resilient sleeves are put undercompressive force, the pressure exerted on the endmost ones istransmitted in turn to the innermost ones, substantially evenly, withoutoverstressing the resilient material in any of their local areas, suchfor instance adjacent the ends where the force is applied and withoutunderstressing the material, for instance at the center, namely, theplace along the length of the mandrel farthest removed from the place ofapplication of the force.

Briefly, my invention contemplates a mandrel for sanding drums of thecharacter indicated comprising central supporting heads about which isplaced a cylinder or shell of steel or the like. Axially disposed shaftsproject outwardly from the heads. Mounted for axial sliding movementupon the inner shell just described is a plurality of individual,separate, relatively short cylinders or sleeves of metal such asaluminum. On the outer surfaces of said sleeves are bonded cylinders ofelastomeric material such as rubber or one of the synthetic rubbers.lnterposed between each of these aluminumrubber units is a washer, thewashers being reduced in thickness in those radial areas thereof whichare adjacent the ends of the aluminum cylinders. The shafts supportingthe mandrel have threaded sections to receive nuts. lnterposed betweenthe nuts and the outermost ones of the aluminum-rubber units is a spacerwasher adapted to slide up in the ends of the sleeve, into contact withthe ends of the rubber cylinders at the ends of the mandrel and to exertpressure on the endmost ones of the rubber bodies when the nuts aredrawn up. The pressure exerted on the rubber by these washers in turn isexerted on the outer radial portions of the spacer washers between thealuminum-rubber units which in turn transmits this pressure to the nextrubber unit, and so forth. The aluminum sleeves to which the rubbersections are bonded are free to move toward each other in response tothe endwise pressure, as permitted by the reduced thickness of thespacer washers. Thus, with the sleeve in place about my improvedmandrel, the nuts are run up and the rubber sections are expandedequally, evenly and quite accurately in a radial or outward direction,thus to engage and support the sanding drum from its inner surfaces. Theparts are so dimensioned that when in relaxed condition the spacerwashers are slightly greater in diameter than the surface of the rubbersleeves so that when the sanding cylinder is moved axially of themandrel it slides on the peripheries of the washers rather than on therubber, facilitating the slipping of the same on or off the mandrel. Asan added feature I propose to provide a shoulder on the inner steelcylinder, at the longitudinal midpoint thereof against which theinnermost ones of the aluminum cylinders engage, upon full compressionof the resilient material thereby to transmit the force from a giventake-up nut only one-half the length of the mandrel.

Apparatus illustrating features of my invention is shown in theaccompanying drawing, forming a part of this application, in which:

FIG. 1 is a side elevational view of my improved mandrel with a sandingdrum thereon, the supporting shafts being broken away and in section;

FIG. 2 is an enlarged detail sectional view taken generally along line2-2 of FIG. 1, the thickness of the shell of the sanding drum beinggreatly exaggerated;

FIG. 3 is an enlarged detail sectional view taken generally along line3-3 of FIG. 1; and,

FIG. 4 is a fragmental detail sectional view corresponding to a portionof FIG. 2 and showing the mandrel in relaxed position, that is, inposition for the sanding drum to be removed.

Referring now to the drawings for a better understanding of my inventionI illustrate the same as being adapted to receive and rotate a sandingdrum 10. This sanding drum may embody a relatively thin shell, made ofsteel, on the order of 1000 of an inch in thickness to the outer surfaceof which are copper brazed abrasive particles. It is the function of myinvention to permit this shell to be assembled about the mandrel,whereby upon running in on the clamping mechanisms the rubber membersexpand radially, thus frictionally to secure the drum to the mandrel forrotation during sanding.

My improved mandrel comprises generally an inner cylindrical member 11which has heads 12 and 13 secured therein as by welding. Secured to theheads 12 and 13 are shafts 14 and 16, having threaded sections 14a and16a and reduced sections 14b and 16b passing through bearings, notshown, and one of which may be a driving shaft.

Slidably mounted on the exterior surface of the cylinder-like supportingmember 11 are metal cylinders 17. In view of the fact that these are allduplicates, a description of one will suffice for all. First, each ofthe metal cylinders 17 carries sleeves 18 of elastomeric material suchas rubber. Preferably, this rubber is vulcanized to the outer surfacesof the sleeves 17. As best shown in FIG. 4 when in relaxed condition therubber members are slightly longer, axially, than the sleeves 17. Thisis'for a purpose later to appear.

Spaced between each of the units comprising the members 17-18 is aspacer washer 19. These washers 19 have axially reduced or thinnedsections 19a of a radial extent to permit the metallic sleeves 17 to bepressed thereagainst as shown in FIG.'2, which is the position of theparts with the sanding sleeve secured in place. Radially outwardly ofthe thinner sections 19a the washers 19 are thickened, axially, as shownand it is these thickened sections which are engaged by the rubbermembers when the compressive forces are placed on the endmost rubbermembers 18.

In order to prevent members 17 and rubber members 18 carried therebyfromrotating relative to the sup porting cylinder-like member 11, I providea keyway 21 in the outer surface of the member 11 and similar keyways 22in each of the members 17. As shown in FIG. 2 this keyway is interruptedlongitudinally of the cylinder-like member 11 by a radial shoulder 23.Keys 24 are placed in the keyway sections so as to lock the members17-18 against rotation.

Slidably mounted on the ends of the cylinder-like member 11 arecompression washers 26 and 27, so dimensioned as to slide freely up intothe ends of the sanding drum 10. Furthermore, these members have annularpads 26a and 27a respectively which are adapted to engage the rubbermembers 18. Nuts 28 and 29 are provided for threaded engagement with there-' spective threaded sections 14a and 16a and these may have toolseats 28a and 29a to receive a spanner wrench or the like.

It will be noted from FIG. 4 that when in relaxed condition, that is,when the nuts 28 and 29 are screwed away from the ends of the mandrel,the washers 19 are slightly greater in diameter than the diameters ofthe rubber members 18. Therefore, when removing and addingsleeves thesleeves slide on the outer surfaces of the washers, reducing thefriction required to take the sleeves off or put them on.

Preferably, the cylinder-like member 11, the cylinders 17 and thewashers 19 are all made of some material which is a good conductor ofheat, for instance, aluminum.

From what has been described it is now possible more fully to explainthe construction, function and advantages of my invention. Starting withthe nuts 28 and 29 backed off sufficiently to let the parts assume theposition of FIG. 4, a sanding drum 10 may be slipped over the mandrel,from either end depending, of course, upon taking the supporting shaftsout of their bearings or otherwise making the arbor accessible. Insliding onto the mandrel, in view of the fact that the outer diametersof the washers 19 project past the outer diameters of the rubber members18, the sleeve slides quite easily and friction-free into proper axialposition on the mandrel. The nuts '28 and 29-are nowrun up until theseries of sleeve-rubber members, 17-18, arebrought together as shown inFIG. 2, namely, until the metal sleeves 17 come chock-a-block with thethin sections 19a of the washers 19. By this time the rubber members,each of which is slightly longer than its associated member 17, flowsoutwardly, that is radially, into tight, frictional engagement with theinner surface of the sanding drum 10. In view of the provision of theshoulder 23 it will be seen that each end of the mandrel, insofar asengaging the sleeve 10 is concerned is independent of the other.Furthermore, by using a plurality of the separately formed members17-18, and permitting the compressive forces of the endmost rubbermembers 17 to be transmitted to the next one, etc., I have found thatlocal overstressing of the sanding drum 10 is eliminated, therebyavoiding undesirable bulges in its outer sanding surface which wouldcause grooving or other imperfections in the work being sanded. Stillfurther, the heat dissipation from the working surface of the drum 10 tothe rubber and all the other parts is greatly facilitated by making themetal parts of the mandrel of aluminum.

Because the washers 19 are slightly greater, on the order of 20/1000inch overall, in diameter, than the rubber members 18, when in relaxedposition, a sanding drum placed on the mandrel in relaxed condition issubstantially centered and substantially balanced. In other words, arelatively small amount of radial displacement of the rubber isrequired, and this itself makes my improved arbor not only selfcentering with respect to its sanding drum, but also practically assuresdynamic balance of the same.

In view of the foregoing it will be seen that I have devised an improvedmandrel for sanding drums and the like. In actual practice my inventionhas proven to be extremely practical. Instead of using a continuousrubber member, extending from end to end, the individually formed,separate members 17-18 in combination with means to apply compressiveforce to each end of the series of the same results in even,substantially equally distributed outward pressure on the sanding drum,securely holding it without causing local bulging of the same.

While I have shown my invention in but one form, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various other changes and modifications without departing from thespirit thereof.

What I claim is:

1. In a mandrel for supporting sanding drums and the like,

a. an inner cylinder-like member,

b. means supporting said member for powered rotation about itslongitudinal axis,

0. a plurality of metal cylinders slidably mounted on the outer surfaceof said member,

d. sleeves of elastomeric material surrounding each of said metalcylinders,

e. spacer rings having inner sections interposed between the adjacentends of the metal cylinders and which are a fraction of an inch greaterin diameter than the diameters of said sleeves of elastomeric materialwhen the latter are in relaxed condition,

and

f. means engaging-the endmost ones of said elastomeric sleeves anddisposed to exert inward, axial pressure thereon, whereby such pressureis transmitted through the endmost elastomeric sleeves to the adjacentspacer ring thence to the next elastomeric sleeve, and so forth, causingthe elastomeric sleeves to distort radially, thereby frictionally toengage the inner periphery of a cylindrical sanding drum placed on themandrel.

2. Apparatus as defined in claim 1 in which said inner cylinder-likemember, adjacent its longitudinal center, has a radially extendingabutment against which the adjacent ends of the adjacent metal cylinderscome to rest when said pressure is exerted, and in which the means toexert said pressure comprises a threaded shaft at each end of themandrel, and nuts on the shafts disposed when screwed inwardly of themandrel to exert pressure on the endmost elastomeric sleeves, wherebythe series of elastomeric sleeves on either end of the arbor arestressed independently of each other.

3. Apparatus as defined in claim 1 in which there is means to secure themetal cylinders against rotation relative to the inner cylinder-likemember.

4. Apparatus as defined in claim 3 in which the means to secure themetal cylinders against rotation relative to the cylinder-like membercomprises axially extending keyways in the outer and inner peripheriesof said cylinder-like member and said metal cylinders, respectively, anda key in said keyways.

5. Apparatus as defined in claim 1 in which said elastomeric sleeves arevulcanized to the outer periphery of their associated metal cylinders.

6. Apparatus as defined in claim 1 in which the elastomeric sleeves andspacer washers are so relatively dimensioned that when said pressure isreleased the outer peripheries of said washers lie outwardly of theouter peripheries of said elastomeric sleeves, whereby a sanding drumbeing removed from or placed upon the mandrel slides on said spacerwashers, out of contact with the elastomeric sleeves.

7. Apparatus as defined in claim 1 in which the diameter of said spacerwashers relative to the inner diame ter of the sanding drum to be usedwith the mandrel is such as to substantially center the sanding drum onthe mandrel prior to distorting the elastomeric sleeves into frictionalengagement with the drum.

1. In a mandrel for supporting sanding drums and the like, a. an innercylinder-like member, b. means supporting said member for poweredrotation about its longitudinal axis, c. a plurality of metal cylindersslidably mounted on the outer surface of said member, d. sleeves ofelastomeric material surrounding each of said metal cylinders, e. spacerrings having inner sections interposed between the adjacent ends of themetal cylinders and which are a fraction of an inch greater in diameterthan the diameters of said sleeves of elastomeric material when thelatter are in relaxed condition, and f. means engaging the endmost onesof said elastomeric sleeves and disposed to exert inward, axial pressurethereon, whereby such pressure is transmitted through the endmostelastomeric sleeves to the adjacent spacer ring thence to the nextelastomeric sleeve, and so forth, causing the elastomeric sleeves todistort radially, thereby frictionally to engage the inner periphery ofa cylindrical sanding drum placed on the mandrel.
 2. Apparatus asdefined in claim 1 in which said inner cylinder-like member, adjacentits longitudinal center, has a radially extending abutment against whichthe adjacent ends of the adjacent metal cylinders come to rest when saidpressure is exerted, and in which the means to exert said pressurecomprises a threaded shaft at each end of the mandrel, and nuts on theshafts disposed when screwed inwardly of the mandrel to exert pressureon the endmost elastomeric sleeves, whereby the series of elastomericsleeves on either end of the arbor are stressed independently of eachother.
 3. Apparatus as defined in claim 1 in which there is means tosecure the metal cylinders against rotation relative to the innercylinder-like member.
 4. Apparatus as defined in claim 3 in which themeans to secure the metal cylinders against rotation relative to thecylinder-like member comprises axially extending keyways in the outerand inner peripheries of said cylinder-like member and said metalcylinders, respectively, and a key in said keyways.
 5. Apparatus asdefined in claim 1 in which said elastomeric sleeves are vulcanized tothe outer periphery of their associated metal cylinders.
 6. Apparatus asdefined in claim 1 in which the elastomeric sleeves and spacer washersare so relatively dimensioned that when said pressure is released theouter peripheries of said washers lie outwardly of the outer peripheriesof said elastomeric sleeves, whereby a sanding drum being removed fromor placed upon the mandrel slides on said spacer washers, out of contactwith the elastomeric sleeves.
 7. Apparatus as defined in claim 1 inwhich the diameter of said spacer washers relative to the inner diameterof the sanding drum to be used with the mandrel is such as tosubstantially center the sanding drum on the mandrel prior to distortingthe elastomeric sleeves into frictional engagement with the drum.